Self-organizing fuzzy controller for injection molding machines

Most plastic parts are manufactured using an open-loop injection molding machine (IMM). However, this process produces parts with poor dimensional precision and may result in product shrinkage, residual stress and other effects depending on the complexity of parts' geometric shape, size, or a combination of both. To improve the performance of the IMM, in this study, we modified the IMM's control structure from open-loop to closed-loop. The IMM has clearly complicated and nonlinear characteristics. Thus, it is difficult to design model-based controllers for manipulating the IMM. To solve the problem, a model-free self-organizing fuzzy controller (SOFC) was developed to control the IMM and its control performance was evaluated. Experimental results demonstrated that the SOFC exhibits better control performance than the fuzzy logic controller or the proportional-integral-derivative (PID) controller in controlling the injection-screw velocity of the IMM and the injection-nozzle holding pressure of the IMM.